Gibbon

Gibbons are small, tailless apes of the family Hylobatidae, split into four genera and 20 species. They live in subtropical and tropical forests from eastern Bangladesh and Northeast India to Southeast Asia and Indonesia, including Sumatra, Borneo and Java. They move by brachiation, swinging from branch to branch, and form long-term pair bonds, unlike most great apes. Groups are strongly territorial and defend their boundaries with visual and vocal displays. A mated pair duets, sometimes joined by their young, and the song can often be heard for distances up to 1 km. Fur ranges from dark to light brown and any shade between black and white.

About the gibbon

A gibbon is a small, tailless ape from the tropical forests of Southeast Asia, known for swinging arm over arm through the trees and for its loud singing. Gibbons make up the family Hylobatidae, the "lesser apes," and are close relatives of the great apes and humans. They range from northeast India to Indonesia.

Gibbons differ from the great apes, such as orangutans and chimpanzees, in being smaller, in males and females looking much alike, and in not building nests. Their lineage split from the great apes around 16.8 million years ago, making gibbons the first apes to branch off from the common ancestor of humans and great apes. Their genome is about 96 percent similar to ours.

The family has four genera, told apart by chromosome number: Hylobates, the dwarf gibbons, which include the white-handed gibbon or lar gibbon; Hoolock, the hoolock gibbons; Nomascus, the crested gibbons, including the white-cheeked gibbons; and Symphalangus, which holds a single species, the siamang. The siamang is the largest gibbon, and two toes on each of its feet are joined together, which is where its scientific names come from.

Gibbons weigh 3.9 to 12.7 kg (8.6 to 28 lb). Their arms are remarkably long, and their hands and feet are long and thin, with a deep cleft between the first and second digits of the hand. Fur is usually black, grey or brownish, often with white on the hands, feet and face, and depending on species and sex it can be any shade from dark brown to almost white. A completely white gibbon is rare.

The wrist is the key to how gibbons move. It works like a ball-and-socket joint, rotating in two directions, which saves a great deal of energy in the upper arm and torso and takes stress off the shoulder. Some species, notably the siamang, have a throat sac that inflates into a resonating chamber when they call, sometimes growing as large as the animal's head.

Behavior and diet

Gibbons are active by day and live in the trees; lar gibbons, for example, rarely come down to the ground. Their main way of getting around is brachiation, swinging from branch to branch for up to 15 m (50 ft) at a time at speeds up to 55 km/h (34 mph). They can leap up to 8 m (26 ft) and are the fastest of all tree-dwelling mammals that cannot fly. The lifestyle has a cost: researchers estimate that most gibbons break a bone at least once in their lives when a branch snaps or a hand slips. On the ground, gibbons walk upright with their arms raised for balance.

They live in small family groups, usually two to six related animals. Pairs often stay together for life, though they are not always faithful, and pairs occasionally "divorce." About 10 percent of wild groups studied contained more than two adults.

Gibbons are famous for singing. Groups are strongly territorial and defend their boundaries with loud displays, often a duet between the mated pair that the young sometimes join. The songs can carry up to 1 km (0.6 mi), and they reveal both the species and the region a gibbon comes from. In most species, males and some females also sing solos to attract mates. Gibbon voices are more powerful than any human singer's.

Fruit makes up about 60 percent of the diet, including figs and many other fruits, supplemented by leaves, shoots, twigs, flowers, insects and occasionally birds' eggs. How much fruit they eat depends on what is locally available. Crested gibbons of the genus Nomascus eat the most leaves, likely because their high, seasonal forests lack fruit year-round.

The lar gibbon gives a picture of gibbon family life. It is active for about 8.7 hours a day, leaving its sleeping tree around sunrise. Mating happens year-round, gestation lasts about six months, and a single baby is typical. Young nurse for about two years and are fully mature at around eight. Wild females first give birth at about 11 years old, and wild lar gibbons live about 25 years.

Range and habitat

Gibbons live in subtropical and tropical forests from eastern Bangladesh and northeast India through mainland Southeast Asia to the Indonesian islands of Sumatra, Borneo and Java. They depend on the forest canopy for food, travel and shelter.

Gibbons once lived far more widely. Historical evidence suggests they were widespread in central and southern China until at least the Song dynasty, before habitat destruction wiped them out across most of the country by around the 14th century.

Gibbon vs great ape

Gibbons are apes, not monkeys, but they are different from the great apes in several ways.

Conservation status

There is no single status for gibbons, because the IUCN Red List assesses each species separately. Most species are Endangered or Critically Endangered; the eastern hoolock gibbon, listed as Vulnerable, is the only exception. The white-handed or lar gibbon, for example, was assessed as Endangered in 2020. The main threat is the degradation and loss of their forest homes.

Gibbons are listed on Appendix I of CITES. Rescue groups in Thailand, Borneo and Sumatra rehabilitate gibbons that were kept as pets and release them back into the wild. The IUCN's primate specialist group named 2015 the Year of the Gibbon to raise awareness of their plight.